Molded sonic absorber

ABSTRACT

The present invention provides a molded sonic absorber excellent in sound absorption action for a sound with a wavelength in a human audible range. More specifically, the present invention provides a molded sonic absorber obtained by mixing: a chip of a cellulose acetate fiber as a component (A) ; a chip of a polyurethane foam as a component (B); and a urethane resin-based adhesive as a component (C), followed by compression molding.

FIELD OF THE INVENTION

The present invention relates to a molded sonic absorber, a laminatedsonic absorber, and an interior material for an automobile and the likeusing the absorbers.

PRIOR ART

Conventional sound absorption/sound-insulating material for a vehicle ora dwelling house and the sound absorption material for asound-insulating wall in freeway, are principally glass wool, rock wool,aluminum fiber, lightweight foamcrete, porous ceramic or the like as aninorganic substance. As the organic material, a laminate of polymer foamsuch as foamed urethane with an adhesive such as isocyanate is used forautomobile ceiling as sound absorption/sound insulating material. Soundabsorption panel with fibrous body composed of an organic material isput to practical use, too.

However, a satisfactory sound absorption material could not be obtainedin terms of an improvement in workability, prevention of an obstacle tothe human body, environmental protection, and easy processing andpotential for recycling of waste for efficient utilization of resources.The range of 400-1000 Hz is included in the range of human voice. Thesense of hearing is more sensible to this range than the normal soundarea. A person feels fatigued to noise including this range tiring.Therefore, a material that efficiently absorbs a noise in theabove-mentioned frequency range has been demanded, but there has been nomaterial that can satisfy the demand.

JP08-87278A, JP08-87279A, JP10-77562A, and JP10-110370 A have been knownas the related prior arts.

JP 08-87278 A discloses a sound absorption sheet structured by a poroussound absorption body in which a porosity of a sound absorption layerincreases as the layer approaches an outer surface. This inventionenhances a sound absorption effect. However, a constitution of thisinvention is complicated, leading to poor practicability.

JP 08-87279 A discloses a method of uniformizing a sound absorptionfrequency range by laminating sound absorption materials of differentsound absorption frequency ranges. However, this invention requires thefollowing steps of: producing sound absorption materials of differentsound absorption frequency ranges; and laminating the sound absorptionmaterials, and therefore results in poor productivity.

JP 10-77562 A and JP 10-110370 A each disclose a manufacturing techniquefor a sound absorption material made of a fibrous body. Those inventionseach disclose a sound absorption material which is structured by two ormore kinds of fibers and in which a part of the constituent fibers arethermally fused. However, in order to adopt such a structure, the fibersmust adopt a two-layer structure (a core/sheath structure) made up of acenter layer and a surface layer. Therefore, a special apparatus isneeded in producing the fibers. None of those inventions is general.

None of the above four inventions discloses use of a wate material orthe like.

JP 08-84982 A discloses a method of recycling waste including: crushingdiscarded materials generated from automobiles and buildings into finepieces; mixing the fine pieces with a binder; clamping the mixture byusing a net-shaped material (for instance, a metal gauze or a punchingmetal) through which air can permeate; and molding the mixture underheating by allowing hot air to pass through the net-shaped material, sothat the molded object is applicable to the sound absorption material orthe like. However, a mesh in the metal gauze or the punching metal forclamping the finely crushed pieces is extremely small, and soundabsorption performance is anticipated to deteriorate. The publicationdiscloses nothing about a specific sound absorption effect.

JP 07-205169 A discloses a method of producing a molded soundproofmaterial including: crushing discarded materials generated fromautomobiles and buildings; mixing the crushed product with a fibrousbinder; evenly dispersing the mixture in water; subjecting thedispersion to dehydration and heating; and molding the resultant productunder heating and pressure into a molded soundproof material. However,this method involves a problem in that the production process iscomplicated. The publication discloses nothing about a specificsoundproofing effect of the resultant molded soundproof material.

JP03-7739A discloses a technique in which a ground material ofpolyurethane scrap is added and mixed with a prepolymer composed of adiol and an isocyanate using a binder, and in which the whole issubjected to molding under heating and pressure. However, thepublication discloses nothing about a sound absorption effect.

DISCLOSURE OF THE INVENTION

A purpose of the present invention is to provide a sound absorptionmaterial and a laminated sonic absorber each of which is excellent insound absorption property particularly in a human audible frequencyrange, and an interior material for an automobile and the like using theabsorbers.

As means for solving the above problems, the present invention providesa molded sonic absorber containing (A) a chip of an organic or inorganicfibrous body and (B) a chip of an organic or inorganic porous body.

The phrase “fibrous body” as used herein refers to a molded objectcontaining an organic or inorganic fiber, and the shape, size, or thelike of the molded object is not particularly limited.

The term “chip” as used herein as against fibrous body includes: aground, cut, cracked, or crushed product obtained by application of amechanical means; one originally present as a chip in a fibrous bodysuch as a fragment generated during the production processing; and afibrous body molded into a chip. The shape and size of a chip are notparticularly limited, but the chip preferably has a maximum length of 20mm or less.

As other solving means, the present invention provides a laminated sonicabsorber having two or more layers including the above molded sonicabsorber and a foam in the form of a laminate.

The above molded sonic absorber or laminated sonic absorber isapplicable to an interior material for an automobile, to a buildingmaterial, and to a sound absorption structure. The term “structure” inthe phrase “sound absorption structure” means a structure having a flator solid shape in accordance with its application, and includes astructure of a desired shape such as a panel-like shape or acabinet-like shape.

The phrase “sound absorption” as used herein refers to a property thatacts to reduce the loudness level, and differs from a sound insulatingaction only for insulating a sound.

Examples of the chip of an organic fibrous body as the component (A) inthe molded sonic absorber of the present invention include chips madefrom a thermoplastic resin, a thermosetting resin, a natural polymer,and a semisynthetic polymer.

Examples of the thermoplastic synthetic polymer include: polyolefin madeof polyethylene, polypropylene, poly-4-methylpentene-1, and the like;ethylene-based copolymers such as an ionomer, an ethylene-vinyl acetatecopolymer, an ethylene-methyl methacrylate copolymer, an ethylene-ethylacrylate copolymer, and an ethylene-acrylic acid copolymer; halogencopolymers such as polyvinyl chloride or polyvinylidene chloride; an ASresin; an ABS resin; and polystyrene.

Examples of the thermosetting synthetic polymer include an epoxy resinand an unsaturated polyester resin. Examples of the natural polymerinclude cellulose, cotton, silk, wool, and hemp. Examples of asemisynthetic fiber include cellulose nitrate, cellulose acetate,cellulose acetate propionate, cellulose acetate butyrate, and ethylcellulose.

Examples of the chip of an inorganic fibrous body include chips madefrom glass wool, rock wool, an aluminum fiber, and a boron fiber.

In the case where a thermoplastic synthetic polymer is used as thecomponent (A), a thermoplastic synthetic polymer having a high meltingpoint is preferable. Many thermoplastic synthetic polymers have lowmelting points, and deform when heated in compression molding or thelike treatment upon molding. Therefore, the shape of the fibrous bodymay not remain as it is, which may adversely affect the sound absorptionperformance.

In the case where a thermoplastic synthetic polymer is used as thecomponent (A), preferable is a thermoplastic synthetic polymer providedwith heat resistance comparable to that of a polyethylene terephthalateresin or a nylon 6 resin. However, a thermoplastic polymer compoundhaving a lower melting point (for example, a polyethylene or anethylene-based copolymer) can be used from the standpoint of utilizingwaste as a raw material. In that case, it is desirable to adjust themelting point of the thermoplastic polymer compound and the content ofthe component (A).

In the case where a thermoplastic polymer compound having a low meltingpoint is used, a thermoplastic polymer having a melting point in thetemperature range of 80 to 110° C. is used. In addition, the content ofthe thermoplastic polymer compound in the component (A) is 20% by massor less, preferably 15% by mass or less, more preferably 10% by mass orless, still more preferably 5% by mass or less, and particularlypreferably 3% by mass or less.

In the case where a thermoplastic polymer compound having a low meltingpoint is used as the component (A), it is desirable to adjust theheating temperature and heating time of the polymer compound incompression molding treatment according to the melting point and contentof the polymer compound. If a thermoplastic polymer compound having alow melting point is used as the component (A), and the heatingtemperature and heating time of the polymer compound in compressionmolding treatment are adjusted, the polymer compound fuses to act as abinding agent or an adhesive. Therefore, a binding agent as a component(C) can be unnecessary, or the usage amount of the binding agent can bereduced. Furthermore, the sound absorption performance is not damaged byvirtue of the action of the component (A) as the residue.

The component (A) preferably has high hardness to enhance the soundabsorption performance. From such a point of view, cellulose acetatefibers, which are semisynthetic polymers, are preferable.

The cellulose acetate fibers are classified into a cellulose diacetatefiber and a cellulose triacetate fiber. Among them, the cellulosediacetate fiber is preferable. The cellulose diacetate fiber has higherhydrophobicity than that of a natural fiber, has lower hydrophobicitythan that of a synthetic fiber, and thus has appropriate hygroscopicityand hydrophobicity. Therefore, moisture itself of the fiber which hasappropriately taken up moisture acts to enhance the sound absorptionperformance, which is preferable.

In the case where a cellulose acetate fiber is used as the component(A), preferable is a cellulose acetate fiber containing an acetatefilament (continuous fiber), an acetate tow obtained by bundling theacetate filament, or an acetate staple (short fiber). Those fibers maybe crimped or may not be crimped. However, a crimped acetate staple ispreferable in terms of air permeability and moisture retention.

A waste material such as a scrap fiber generated in a staple factory orthe like or a scrap filter generated in a cigarette filter factory canbe used as the cellulose acetate fiber. Among them, the scrap filter ispreferable because every filter is cut into an equal fiber length andthe cellulose diacetate fiber is used as a raw material. Those celluloseacetate fibers are preferably well disentangled before use by using acard or the like to enhance dispersibility in the molded sonic absorber.

In the case where a scrap filter for a cigarette is used, paper formingthe filter (cigarette filter roll paper) is included in the component(A). Such a paper component accounts for less than 80% by mass,preferably 50% by mass or less, more preferably 40% by mass or less,still more preferably 30% by mass or less, particularly preferably 10 to20% by mass, and most preferably 12 to 18% by mass of the component (A).

In the case where the paper content resulting from the raw material isgreat, a paper removing operation may be performed, or the component (A)containing no paper may be added separately. However, from the viewpointof reducing waste and effectively utilizing resources, such a materialmay be applied as a production raw material for use in an applicationwhere the sound absorption performance is not required to a largeextent. For example, such a material may be applied as a production rawmaterial for use in an application where a heat insulating property ishighly required rather than the sound absorption property.

The component (A) may be one containing a short fiber, a continuousfiber, or a mixture thereof.

With regard to the size (for a fiber, a fiber length) of the chip as thecomponent (A), its maximum length is preferably 20 mm or less, morepreferably 1 to 20 mm, still more preferably 5 to 20 mm, particularlypreferably 10 to 20 mm, and most preferably 10 to 15 mm in order toenhance the dispersibility and the sound absorption performance.

The maximum length as used herein refers to a maximum value for a majoraxis of an island part (a domain) in the case where an area that hasbeen subjected to molding under heating is taken with a known imagecapturing device, and is subjected to two-dimensional processing with animage processing device or the like.

A degree of fineness of the component (A), which is not particularlylimited, is selected preferably from the range of 1.5 to 10 deniers,more preferably from the range of 2 to 8 deniers, and still morepreferably from the range of 2.5 to 5 deniers. Fibers of differentdegrees of fineness may be mixed and used.

A sectional form of the component (A) is not particularly limited, butis preferably of a Y shape in terms of sound absorption performance anduse of a cigarette filter provided as waste.

The component (A) may contain a component originating from a rawmaterial. For instance, the component (A) may contain industrial wastesuch as rag opening, waste cotton, or a scrap fiber of a natural fiberto be disposed of as industrial waste or the like. As a matter ofcourse, the component (A) may contain a scrap fiber of a syntheticfiber.

The component (B) in the molded sonic absorber of the present inventionis an organic or inorganic porous body. Pores in the porous body may beindependent of or continuous with each other. Examples of the inorganicporous body as the component (B) include activated carbon includingcharcoal, pumice, foamcrete, and sintered clay. Examples of the organicporous body include foams such as a polyethylene foam, a polystyrenefoam, and a polypropylene foam.

A porous foam of the component (B) preferably uses at least an organicfoam, in particular a polymeric foam rather than be composed only of aninorganic foam. A porous foam composed only of an inorganic foam makesit difficult to integrate the component (A) and the component (B), withthe result that the strength of the resulting molded sonic absorberdeviates from a practical range.

In the case where a mixture of an inorganic foam and an organic foam isused as the component (B), it is advantageous to set the content of theinorganic foam to be 20% by mass or less of the entire foam in terms ofintegration.

A thermoplastic polymeric foam such as a polyethylene foam or apolystyrene foam can be used as the polymeric foam. However, using afoam composed of a thermosetting resin provides a more preferable effectin terms of sound absorption performance. When a thermoplastic polymerfoam is heated in compression molding, it may be deformed and a voidratio rate thereof may decrease. Sound absorption ability over the wholesound wave region may be easily lost. This case, however, is not so badas the fibrous body.

A polyurethane foam (a urethane foam) can be given as a particularlypreferable thermosetting polymeric foam, and particularly, athermosetting polymeric foam composed of a soft polyurethane foam thatis a foam obtained via a reaction between a polyol and an isocyanate. Inthe case where an adhesive is used to strongly integrate the component(A) with the component (B), the polyurethane foam is excellent inaffinity with the adhesive and wettability. In addition, thepolyurethane foam imparts strength, hardness, and durability to themolded sonic absorber, and is thus preferable.

The polyurethane foam serving as a raw material for the component (B)may be, for example, a scrap generated in a foaming process, a trim ofurethane foaming, one used as a buffer material for baggage or the like,or one used as a filler for furniture or the like. A ground product ofurethane and a compressed urethane chip which have been recovered fromwaste products such as home appliances, in particular a refrigerator,may be also used. For example, in the case of a refrigerator, a heatinsulating material is sorted out through manual disassembly, urethaneis sorted out by means of wind force, and urethane is ground into chipswith a crusher. Each of these ground products may be used as apolyurethane foam. Alternatively, compressed urethane chips obtained byappropriately compressing those ground products may be used.

A density of the component (B) is preferably in the range of 0.015 to0.03 g/cm³, more preferably in the range of 0.015 to 0.025 g/cm³, andstill more preferably in the range of 0.015 to 0.02 g/cm³.

In the case where a polyurethane foam is employed as the component (B),a polyurethane foam molded product mechanically formed in to a chipthrough cutting, grinding, cracking, crushing, or the like may be used.In addition, a polyurethane foam molded product molded into a chip maybe used.

The shape of the chip of the component (B) is not particularly limited,but the chip has a maximum length of preferably 20 mm or less, morepreferably 5 to 20 mm, and still more preferably 10 to 15 mm.

A maximum length of 20 mm or less not only enhances the dispersibilityof the component (B) in the molded sonic absorber but also reduces arestoring property thereof upon molding. As a result, mold abilityincreases, and maldistribution of the sound absorption performance oncompletion of a molded object reduces. Setting the lower limit to 5 mmor more results in a good mixing property of the component (A) and thecomponent (B) and a reduction in maldistribution of the sound absorptionperformance, and is thus preferable.

In order to enhance the sound absorption performance, the content of thecomponent (A) is preferably 80 to 20% by mass, more preferably 70 to 30%by mass, still more preferably 60 to 40% by mass, and particularlypreferably 45 to 55% by mass, whereas the content of the component (B)is preferably 20 to 80% by mass, more preferably 30 to 70% by mass,still more preferably 40 to 60% by mass, and particularly preferably 55to 45% by mass.

If the content of the component (A) is 80% by mass or less and thecontent of the component (B) is 20% by mass or more, the component (A)and the component (B) can be mixed uniformly and a mixing property witha binding agent is satisfactory. As a result, moldability increases. Ifthe content of the component (A) is 20% by mass or more and the contentof the component (B) is 80% by mass or less, the sound absorptionperformance can be enhanced. Therefore, suitable performance for a soundabsorption material can be maintained. If the contents of the component(A) and the component (B) are within the above ranges, a balance amongthe sound absorption property, strength, and hardness of the moldedobject obtained from those materials can be established.

In the molded sonic absorber of the present invention, the component (A)and the component (B) are integrated, and a binding agent as thecomponent (C) can be used in combination with these components as amaterial making up for the integration. The binding agent is notparticularly limited as long as the binding agent has tackiness, but anadhesive is particularly preferable.

Examples of the adhesive include hydrophilic polymer-based andhydrophobic polymer-based adhesives such as a vinyl acetate-basedadhesive, a polyvinyl alcohol-based adhesive, a cellulose-basedadhesive, an olefin resin-based adhesive, an epoxy resin-based adhesive,a nitrile rubber-based adhesive, and a urethane resin-based adhesive.

Of those, in order to obtain sufficient tensile and flexural strengthsand appropriate hardness on completion of a molded object, hydrophobicpolymer-based adhesives such as an epoxy resin-based adhesive, a nitrilerubber-based adhesive, and a urethane resin-based adhesive arepreferable, and a urethane resin-based adhesive is the most preferable.

Examples of the polyol used for synthesizing a urethane resin-basedadhesive include a polyether polyol and a polyester polyol, thepolyether polyol is preferred. The polyether polyol to be used isprepared as follows. First, a polyhydric alcohol such as polypropyleneglycol, glycerin, diglycerin or pentaerythritol, or an amine such asethylenediamine or ethanolamine is provided as the starting material.Then, the starting material is subjected to ring-opening polymerizationwith an alkylene oxide such as ethylene oxide or propylene oxide. Apolyol with a number average molecular weight in the range of 200 to10,000 is preferable. Examples of the isocyanate used for synthesizing aurethane resin-based adhesive include aromatic isocyanates typified bytolylene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI).

The content of the binding agent (adhesive) is preferably 10 to 30 partsby mass, more preferably 15 to 30 parts by mass, and still morepreferably 20 to 25 parts by mass with respect to 100 parts by mass ofthe total of the component (A) and the component (B). A content of thebinding agent of 10 parts by mass or more can maintain a sufficient bondstrength between the component (A) and the component (B). A content ofthe binding agent of 30 parts by mass or less can maintain excellentsound absorption performance.

A porous granular material such as activated carbon or a natural fiberchip such as a paper piece or a non-woven fabric piece can be added asan auxiliary if required to the molded sonic absorber of the presentinvention. In the case where a cigarette filter contains activatedcarbon, its filter scrap can be used as it is. In particular, additionof a paper piece can increase the volume of the molded object withoutaffecting the sound absorption performance.

A blending amount of the auxiliary is preferably 5 to 20 parts by mass,more preferably 7 to 18 parts by mass, and still more preferably 10 to15 parts by mass with respect to 100 parts by mass of the total of thecomponent (A) and the component (B)

The molded sonic absorber of the present invention can be obtained viathe following procedure. A fibrous body as the component (A) and aporous body as the component (B) are separately formed into chips,followed by mixing. Alternatively, both components are mixed and arethen formed into chips through grinding or the like. Subsequently, theresulting mixture of chips is mixed with an adhesive or other auxiliaryif required, and the whole is molded into a desired shape.

Available crushers for forming the component (A) and the component (B)into chips include a rotary crusher and a rag opening crusher.

A method in which molding materials composed of the component (A), thecomponent (B), and, if required, the component (C) are mixed and placedin a vessel of a desired shape, or a method in which molding materialsare subjected to compression molding to provide a desired shape can beapplied to the molding.

The vessel of a desired shape is not particularly limited. For instance,a wood vessel, a plastic vessel, a metallic vessel, and a ceramic vesselcan be used. Furthermore, one obtained from the above molding materialscontaining the component (A) and the component (B) may be used.

Conditions for applying the compression molding method vary slightlydepending on the ratio between the component (A) and the component (B),on the size, thickness, or the like of the molded object, and on thekind of adhesive. For example, for a molded object measuringapproximately 30 cm by 30 cm by 10 cm, the molding is carried out at atemperature of 80 to 110° C. and under a pressure of 98 to 980 kPa (1 to10 kg/cm²) for 3 to 10 minutes.

The molded object has a density preferably in the range of 0.05 to 0.2g/cm³, more preferably in the range of 0.08 to 0.18 g/cm³, and stillmore preferably in the range of 0.12 to 0.18 g/cm³. A density within theabove range can satisfy the sound absorption performance, the strength,and the hardness as well as the lightweight property.

The molded object may be of a desired shape such as a sheet, a plate, acube, a rectangular parallelopiped, a columnar, or a spherical accordingto an application.

A molding method or a slicing method can be applied as a method ofproducing the molded sonic absorber of the present invention. However, amolded object obtained by the molding method offers a good soundabsorption coefficient in the frequency range not lower than 600 Hz ifthe molded object has a high specific gravity.

The reason why the molded sonic absorber of the present invention exertsexcellent sound absorption performance particularly for a sound in ahuman audible range is probably as follows. The shapes of the component(A) and the component (B) constituting the molded sonic absorber are notuniform, resulting in poor uniform dispersibility compared to that of apowder. In other words, the components are partly randomly dispersed ina state where one of the components is slightly unevenly distributed.Therefore, contrarily, the randomly dispersed states of the component(A) and the component (B) synergistically interact in absorbing acousticwave energy in the human audible range and converting the acoustic waveenergy into heat energy, to thereby enhance a sound absorption abilityfor the acoustic wave energy. As a result, the sound absorptionperformance is enhanced.

The molded sonic absorber of the present invention can provide avertical incidence sound absorption coefficient of 0.2 or more,preferably 0.4 or more, at 400 Hz measured according to the verticalincidence sound absorption measurement method (JIS A1405). Moreover, themolded sonic absorber can provide a vertical incidence sound absorptioncoefficient of 0.4 or more in the frequency range of 400 to 1,000 Hz.Preferably, the molded sonic absorber can provide a vertical incidencesound absorption coefficient of 0.4 or more in the frequency range of400 to 550 Hz.

The laminated sonic absorber of the present invention is obtained bylaminating two or more layers including the above molded sonic absorberand a foam. Adjacent layers are bonded to each other with the adhesiveor the like.

The foam in the laminate may be one composed of a component identical tothe component (B). The shapes and sizes of the molded sonic absorber andthe foam can be determined depending on applications. Two or more foamsdifferent from each other in thickness and density may be combined andlaminated.

The order in which the molded sonic absorber and the foam are laminatedmay be regular or random. In addition, one or two or more molded sonicabsorber layers may be laminated, and similarly, one or two or more foamlayers may be laminated. For example, a molded sonic absorber and a foammay be alternately laminated. Alternatively, a foam may serve as anintermediate layer with molded sonic absorbers laminated on its bothsides. Contrarily, a molded sonic absorber may serve as an intermediatelayer with foams laminated on its both sides.

A support layer and/or a protective layer may be laminated on one orboth faces of the laminate.

The support layer is made from a metallic plate, a plastic plate, a woodplate, a ceramic plate, a woven fabric, a non-woven fabric, cardboard,paper, or the like. When mounting a laminate on an automobile ceilingface, an interior wall surface, or the like, the support layer forms abonding layer between the laminate and the automobile ceiling face, theinterior wall surface, or the like.

When mounting a laminate on an automobile ceiling face, an interior wallsurface, or the like, for example, the protective layer faces theinterior. The protective layer can be made from the same material asthat for the support layer. However, the protective layer is preferablymade from a woven fabric, a non-woven fabric, or the like from theviewpoint of enhancing the sound absorption performance.

Examples of the laminated sonic absorber include one with a molded sonicabsorber having a density of approximately 0.10 g/cm³ arranged on itssound absorption face side and with a molded sonic absorber having adensity lower than the above density assembled on its back face side. Inthis case, the lower the density of the latter layer, the more excellentthe sound absorption performance.

For example, a laminated sonic absorber with a molded sonic absorberhaving a thickness of approximately 10 mm and a density of 0.10 g/cm³arranged on its sound absorption face side and with a molded sonicabsorber having a thickness of 25 mm and a density of 0.15 g/cm³arranged on its back face side is compared with an entire molded sonicabsorber having a thickness of 35 mm and a density of 0.10 g/cm³. Inthis case, the laminated sonic absorber is superior in strength andhardness to the entire molded sonic absorber. Therefore, the laminate oftwo or more layers different from each other in density is preferablebecause of its application to a wider range of use.

The molded sonic absorber or laminated sonic absorber of the presentinvention is applicable to an interior material for an automobile, abuilding material, a sound absorption structure, or the like.

In the case where the molded sonic absorber or laminated sonic absorberof the present invention is used for a ceiling material for anautomobile, the molded sonic absorber or the laminated sonic absorber isplaced on an automobile ceiling face. Then, a hot melt powder or a hotmelt film is applied onto the surface of the molded sonic absorber.Furthermore, a material to serve as a protective layer such as anon-woven fabric or a textile is laminated on the surface, followed bymolding under heating. As a result, a desired deep drawing shape (havinga depth of about 150 mm) can be obtained. In this case, a woven fabricor a non-woven fabric is suitable for the protective layer. A syntheticleather such as vinyl chloride imparts the sound absorption performance.

In addition, the molded sonic absorber or laminated sonic absorber ofthe present invention is applicable to, for example, a wall surface, aceiling material, a partition wall, a partition, or an interiordecorative material in a house, an office, a factory, a laboratory, acompressor, a motor, or an outdoor heat exchanger of an air conditioner.The molded sonic absorber or laminated sonic absorber of the presentinvention provides not a sound insulating action but a sound absorptionaction. Therefore, the molded sonic absorber or laminated sonic absorberof the present invention can exert excellent sound absorptionperformance even when used in a partition form as mentioned above.

When the molded sonic absorber or laminated sonic absorber of thepresent invention is used outdoors, or is used in a factory, alaboratory, or the like, the molded sonic absorber or laminated sonicabsorber is expected to often contact a hard substance. Therefore, apunching metal maybe used as the protective layer. In the case where apunching metal is used, a punch (hole) area preferably accounts for 40%or more, more preferably 60% or more of the whole punching metal area.This is because both the protective function and the sound absorptionperformance can be obtained. In such a case, additionally affixing adimple sheet on the support layer side enhances the sound absorptionperformance in a frequency range near 500 Hz, and also enhances thesound absorption performance in a high frequency range not lower than1.5 kHz.

A molded sonic absorber constituted by a cellulose acetate fiber issuitable for an interior application requiring hygroscopicity becausecellulose acetate does not swell even if the cellulose acetate absorbswater. For example, in the case where a molded sonic absorberconstituted by a cellulose acetate fiber is applied to a ceilingmaterial for a vehicle or an interior, the molded sonic absorber doesnot deform when in use, and is capable of absorbing moisture in the airand keeping the absorbed moisture. Therefore, the molded sonic absorbercan serve as an absorbent to exert a condensation preventing function, amoisture conditioning function, and the like. Moreover, the molded sonicabsorber can further enhance its sound absorption performance owing tomoisture absorption itself, in other words, by keeping moisture.

The molded sonic absorber of the present invention may contain somedegree of impurities unless the impurities contain a toxic substance, asits raw material. Therefore, waste can be used for a raw material forthe molded sonic absorber. Furthermore, it is not necessary to disposeof the molded sonic absorber of the present invention after the use. Themolded sonic absorber of the present invention can be recycled asfollows. The molded sonic absorber is washed, is formed into chips witha crusher or the like, and is added with an adhesive if required,followed by remolding. Therefore, the molded sonic absorber of thepresent invention is excellent in terms of both a reduction in rubbishand recycling of resources.

Furthermore, the molded sonic absorber and laminated sonic absorber ofthe present invention can be used for heat insulating materials invarious applications because the molded sonic absorber and laminatedsonic absorber of the present invention can exert a heat insulatingaction as well as the sound absorption action.

The molded sonic absorber and laminated sonic absorber of the presentinvention are excellent in sound absorption performance particularly inthe range of 400 to 1,000 Hz in the human audible range.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a diagram for illustrating an air permeability-measuringapparatus.

EXAMPLES

Hereinafter, the present invention is described in more detail by way ofExamples. However, the present invention is not limited to thoseExamples. Measurement methods in the following Examples and ComparativeExamples are as follows.

(1) Sound Absorbing Performance

Molded objects obtained in Examples and Comparative Examples weremeasured in accordance with JIS A1405:1998 Acoustics-Determination ofsound absorption coefficient and impedance in impedance tubes-Methodusing standing wave ratio.

The size of a sample was pursuant to the description in the section6.1.2 Reference of JIS A1405. A sample cut into a circular form with adiameter of 100 mm and a thickness of 35 mm was used for lowerfrequencies (operating frequency of 100 to 800 Hz). Similarly, a samplecut into a circular form with a diameter of 29 mm and a thickness of 35mm was used for higher frequencies (operating frequency of 800 to 5,000Hz or more). A sample was cut in such a manner that a pressurizingdirection when molding a molded sonic absorber would be an incidencedirection of an acoustic wave.

A sound absorption coefficient, which corresponded to a defined in thesection 3.1 Vertical incidence sound absorption coefficient of JISA1405:1998, was determined in accordance with a method of calculating αof JIS. The sound absorption coefficient was measured at 23° C. and 60%RH. The measurement was performed three times, and the three measuredvalues were averaged. The results are shown in Table 1.

(2) Air Permeability

Each of the molded objects obtained in the examples and comparativeexamples was cut into a disk with a thickness of 3 mm and a diameter of100 mm. The disk was sandwiched between upper and lower transparentplastic tubes as shown in FIG. 1 to prepare a measuring apparatus. Asmoked cigarette was inserted into a hole drilled in the lowertransparent plastic tube of the measuring apparatus to measure a timeperiod (second) from the insertion to leak of smoke from the uppertransparent plastic tube. Transparent and waterproof adhesive tape waswound around the side surface including a connection part between acircumference of the molded object and each of the upper and lowertransparent plastic tubes to prevent smoke leak. The results are shownin Table 1.

Example 1

Used for the component (A) was a ground scrap of a plain cigarettefilter (cigarette filter free of activated carbon) of a crimpeddiacetate tow with a degree of fineness of 3 deniers. The filter had0.09 g of paper (filter roll paper) and 0.55 g of diacetate tow percigarette. The roll paper had a weight ratio of 14% by mass.

Mixed were 50% by mass of the component (A) and 50% by mass of a softpolyurethane foam molded object (measuring 5 cm×10 cm×20 cm and having adensity of 0.020 g/cm³) produced from a propyleneoxide adduct ofglycerin (having a molecular weight of 3,500) and tolylene diisocyanate(TDI) as the component (B). Then, the mixture was ground into chips witha rotary crusher (manufactured by Asai Seisakusho Co., Ltd.) having ablade length of 600 mm in such a manner that the maximum length of thechips would be 20 mm or less.

To 1,480 g of the mixture were added 220 g of a moisture curing typepolyurethane-based adhesive (trade name Ribbon Decks, manufactured byToken Resin Chemistry Co., Ltd.) produced from a propyleneoxide adductof glycerin (having a molecular weight of 3,500) and diphenylmethanediisocyanate (MDI). Then, the whole was uniformly mixed to provide asound absorption material.

The sound absorption material was loaded into a compression moldingmachine with a molding capacity measuring 30 cm×30 cm×3.5 cm. Then,water vapor was added to the material, and the whole was molded for 2minutes at a temperature of 105° C. and under a pressure of 392 kPa (4kg/cm²) into a molded sonic absorber of the present invention having adensity of 0.10 g/cm³ and a thickness of 35 mm. The sound absorptioncoefficient and air permeability of the molded sonic absorber weremeasured.

Example 2

Used for the component (A) was a diacetate staple, a scrap of a crimpedcellulose diacetate tow for a cigarette with a degree of fineness of 3deniers. Then, mixed were 70% by mass of the component (A) and 30% bymass of a soft polyurethane foam molded object (measuring 5 cm×10 cm×20cm and having a density of 0.020 g/cm³) produced from a propyleneoxideadduct of glycerin (having a molecular weight of 3,500) and tolylenediisocyanate (TDI) as the component (B). Then, the mixture was groundinto chips with a rotary crusher (manufactured by Asai Seisakusho Co.,Ltd.) having a blade length of 600 mm in such a manner that the maximumlength of the chips would be 20 mm or less.

To 1480 g of the mixture were added 220 g of a moisture curing typepolyurethane-based adhesive (trade name Ribbon Decks, manufactured byToken Resin Chemistry Co., Ltd.) produced from a propyleneoxide adductof glycerin (having a molecular weight of 3,500) and diphenylmethanediisocyanate (MDI). Then, the whole was uniformly mixed to provide asound absorption material.

The sound absorption material was loaded into a compression moldingmachine with a molding capacity measuring 30 cm×30 cm×10 cm. Then, watervapor was added to the material, and the whole was molded for 2 minutesat a temperature of 105° C. and under a pressure of 490 kPa (5 kg/cm²)into a molded sonic absorber of the present invention having a densityof 0.20 g/cm³. The sound absorption coefficient and air permeability ofthe molded sonic absorber were measured.

Example 3

50% by mass of the component (A) and 50% by mass of the component (B),the component (A) and the component (B) being the same as those ofExample 1, were separately ground into chips with a rotary crusher. Theaverage of the maximum length of the chips from the component (A) andthe maximum length of the chips from the component (B) was 7 mm.Subsequently, the chips were mixed.

5 parts by mass of paper pieces crushed to have a maximum length of 7 mmwere added to 100 parts by mass of the mixture, followed by uniformmixing. Then, 135 g of the same moisture curing type polyurethane-basedadhesive as that of Example 1 was added to 1,215 g of the resultantmixture to provide a sound absorption material.

The sound absorption material was molded under conditions identical tothose of Example 1 into a molded sonic absorber of the present invention(density: 0.15 g/cm³). The sound absorption coefficient and airpermeability of the molded sonic absorber were measured.

Example 4

30 parts by mass of an epoxy-based adhesive (trade name Epikote,manufactured by Shell Chemical Co., Ltd.) blended with a curing agentwas added to 100 parts by mass of a mixture of 50% by mass of thecomponent (A) and 50% by mass of the component (B), the component (A)and the component (B) being the same as those of Example 1. Then, thewhole was uniformly mixed to provide a sound absorption material. Afterthat, the sound absorption material was molded into a molded sonicabsorber of the present invention having a density of 0.20 g/cm³ in thesame manner as in Example 2. The sound absorption coefficient and airpermeability of the molded sonic absorber were measured.

Example 5

The molded sonic absorber obtained in Example 1 was cut into pieces eachhaving a thickness of 15 mm. Subsequently, each of those pieces was cutinto a circular form having a diameter of 100 mm or 29 mm. Then, a soundabsorption performance test was carried out on each of the pieces. Thesound absorption coefficient and air permeability of the molded sonicabsorber were measured.

Example 6

A molded sonic absorber of the present invention was obtained in thesame manner as in Example 1 except that 50% by mass of the samediacetate staple as that of Example 1 and 50% by mass of a polystyrenefoam molded object (measuring 5 cm×10 cm×20 cm) having a density of 0.02g/cm³ were used. The molded sonic absorber had a density of 0.10 g/cm³.The sound absorption coefficient and air permeability of the moldedsonic absorber were measured.

Example 7

The molded sonic absorber of Example 1 (having a density of 0.10 g/cm³)was cut into a layer having a thickness of 10 mm. Similarly, the moldedsonic absorber of Example 2 (having a density of 0.20 g/cm³) was cutinto a layer having a thickness of 25 mm. Those layers were integratedwith an adhesive to provide a laminated sonic absorber (having anoverall thickness of 35 mm). The sound absorption coefficient of thelaminated sonic absorber was measured with the layer having a density of0.10 g/cm³ being the sound absorption face. The sound absorptioncoefficient of the laminated sonic absorber was measured. The soundabsorption coefficient and air permeability of the laminated sonicabsorber were measured.

Example 8

The molded sonic absorber of Example 1 (having a density of 0.10 g/cm³)was cut into a layer having a thickness of 10 mm. Similarly, the moldedsonic absorber of Example 3 (having a density of 0.15 g/cm³) was cutinto a layer having a thickness of 25 mm. Those layers were integratedwith an adhesive to provide a laminated sonic absorber (having anoverall thickness of 35 mm). The sound absorption coefficient of thelaminated sonic absorber was measured with the layer having a density of0.10 g/cm³ being the sound absorption face. The sound absorptioncoefficient of the laminated sonic absorber was measured.

Comparative Example 1

Only the same component (A) as that of Example 1 was used and ground tohave a maximum length of about 12 mm in the same manner as in Example 1.The ground material and the same moisture curing type polyurethane-basedadhesive as that of Example 1 were used to provided a molded object inthe same manner as in Example 2. The molded object had a density of 0.10g/cm³. The sound absorption coefficient and air permeability of themolded object were measured.

Comparative Example 2

The diacetate staple of Example 2 was used, and was pressurized withtriacetin to provide a compressed molded object having a density of 0.1g/cm³ and a thickness of 10 mm. The molded object was laminated on andintegrated with a polystyrene foam (having a density of 0.02 g/cm³ and athickness of 25 mm) to serve as a support layer. The sound absorptioncoefficient of the resultant laminate was measured. TABLE 1 ComparativeExample Example 1 2 3 4 5 6 7 8 1 2 (A) cigarette filter 50 70 50 50 5050 50 50 — 100 % by mass of paper in 14 0 14 0 14 14 14 14 — 0 component(A) (B) soft polyurethane 50 30 50 50 50 — — — 100 — foam polystyrenefoam — — — — — 50 — — — — maximum length of 20 20 7 20 20 20 — — 12 —components (A) and (B) after manufacturing method molding slicingmolding slicing slicing molding slicing/ slicing/ slicing moldinglaminating laminating molded density (g/cm³) 0.10 0.20 0.15 0.20 0.100.10 0.10/0.20 0.10/0.15 0.10 0.10 object thickness (mm) 35 35 35 35 1535 35 35 35 35 sound  400 Hz 0.50 0.30 0.30 0.20 0.10 0.20 0.45 0.350.10 0.06 adsorption  630 Hz 0.70 0.65 0.65 0.50 0.20 0.50 0.70 0.680.10 0.20 coefficicent 1000 Hz 0.80 0.75 0.75 0.60 0.40 0.60 0.80 0.840.20 0.35 air permeability (second) 55 80 72 78 58 80 — — 220 —Each of Examples 7 and 8 is a laminate of sliced products and a densityin each of Examples 7 and 8 is a density for each layer of the two-layerlaminate.

The molded sonic absorbers and laminated sonic absorbers of Examples 1to 8 were excellent in sound absorption performance in the frequencyrange of 400 to 1,000 Hz. Moreover, the molded sonic absorbers inExamples 1 to 6 showed very good air permeability despite theirdensities equal to or greater than each of the densities of ComparativeExamples 1 and 2.

1. A molded sonic absorber comprising: (A) a chip of one of an organicfibrous body and an inorganic fibrous body; and (B) a chip of one of anorganic porous body and an inorganic porous body.
 2. A molded sonicabsorber comprising: (A) a chip of one of an organic fibrous body and aninorganic fibrous body; (B) a chip of one of an organic porous body andan inorganic porous body; and (C) a binding agent.
 3. The molded sonicabsorber according to claim 1, wherein the organic fibrous body as thecomponent (A) contains a polymer fiber that is not thermoplastic.
 4. Themolded sonic absorber according to claim 1, wherein the organic fibrousbody as the component (A) contains a cellulose acetate fiber.
 5. Themolded sonic absorber according to claim 1, wherein the component (A)contains at least one of a short fiber and a continuous fiber and thechip has a maximum length of 20 mm or less.
 6. The molded sonic absorberaccording to claim 1, wherein the organic fibrous body as the component(A) contains a cellulose acetate fiber and the cellulose acetate fiberis derived from a cigarette filter.
 7. The molded sonic absorberaccording to claim 1, wherein the component (A) contains paper.
 8. Themolded sonic absorber according to claim 7, wherein the paper is derivedfrom a cigarette filter.
 9. The molded sonic absorber according to claim1, wherein the porous body as the component (B) contains a foamingpolymer.
 10. The molded sonic absorber according to claim 1, wherein theporous body as the component (B) contains a polyurethane foam.
 11. Themolded sonic absorber according to claim 1, wherein the chip of theporous body as the component (B) has a maximum length of 20 mm or less.12. The molded sonic absorber according to claim 1, wherein the chip ofthe porous body as the component (B) comprises one of a trim in urethanefoaming and a recycled product of a wasted heat-insulating material. 13.The molded sonic absorber according to claim 1, wherein the component(A) accounts for 80 to 20% by mass and the component (B) accounts for 20to 80% by mass.
 14. The molded sonic absorber according to claim 13,wherein the component (A) contains paper at a content of less than 80%by mass.
 15. The molded sonic absorber according to claim 1, wherein acontent of the binding agent as the component (C) is 10 to 30 parts bymass with respect to 100 parts by mass of the total of the component (A)and the component (B).
 16. The molded sonic absorber according to claim1, wherein the molded sonic absorber has a density of 0.05 to 0.2 g/cm³.17. The molded sonic absorber according to claim 1, wherein a verticalincidence sound absorption coefficient at 630 Hz measured according tothe vertical incidence sound absorption measurement method (JIS A1405)is 0.2 or more.
 18. The molded sonic absorber according to claim 1,wherein a vertical incidence sound absorption coefficient at 630 Hzmeasured according to the vertical incidence sound absorptionmeasurement method (JIS A1405) is 0.4 or more.
 19. The molded sonicabsorber according to claim 1, wherein a vertical incidence soundabsorption coefficient in a frequency range of 400 to 1,000 Hz measuredaccording to the vertical incidence sound absorption measurement method(JIS A1405) is 0.4 or more.
 20. The molded sonic absorber according toclaim 1, wherein a vertical incidence sound absorption coefficient in afrequency range of 550 to 800 Hz measured according to the verticalincidence sound absorption measurement method (JIS A1405) is 0.4 ormore.
 21. A laminated sonic absorber comprising two or more layersincluding a molded sonic absorber according to claim 1 and a foam in aform of a laminate.
 22. The laminates sonic absorber according to claim21, further comprising at least one of a support layer and a protectivelayer on one or both sides of the laminate of the two or more layersincluding the molded sonic absorber and the foam.
 23. The laminatedsonic absorber according to claim 22, wherein the foam serves as anintermediate layer with molded sonic absorber layers on both sides ofthe intermediate layer.
 24. An interior material for an automobile usingone of the molded sonic absorber and the laminated sonic absorberaccording to claim
 21. 25. A building material using one of the moldedsonic absorber and the laminated sonic absorber according to claim 21.26. A sound absorption structure using one of the molded sonic absorberand the laminated sonic absorber according to claim 21.